Chu has kept a very low profile during the Solyndra affair, traveling to China and Vienna in September and speaking almost exclusively on other topics within his domain as questions pile up from Congress about the lost $535 million loan guarantee.

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White House spokesman Jay Carney said Friday that Chu has "the president's full confidence." But Chu, the Nobel laureate praised last year for spending weeks in a Houston control room brainstorming up engineering ideas that ultimately helped cap the Gulf of Mexico oil gusher, is not out of the woods.

"Just because you are a Nobel Prize-winning physicist doesn't mean you'd be a good orthopedic surgeon," said one former Bush Energy Department official. "They're different skill sets."

"Impressive credentials, but sadly miscast for the rough and tumble, oft unforgiving world of oil and energy markets and its cast of malign actors," Raymond Learsy, author of "Oil and Finance: the Epic Corruption," wrote in a blog post published Monday on the Huffington Post.

The GOP-led House wants answers on how Chu and the rest of the administration missed — or just ignored — red flags surrounding Solyndra when it won the loan guarantee and then restructured the terms of the loan two years later so that taxpayers were on the hook if the company defaulted.

Rep. Cliff Stearns (R-Fla.), the subcommittee chairman at the center of the House investigation, said Friday that Chu is on very thin ice.

"[Chu] obviously must have known about this," Stearns told WLS radio in Chicago. "If they knowingly broke the law here, that's a serious problem. I think for the secretary, I'd like him to testify what he knew and when he knew it."

Carney said it's no surprise Chu would have made the final call on the loan guarantee.

"[Chu] is the head of that department," Carney said. "The department, which we've made clear, where career professionals have administered the program, reviewed the loan applications and made the recommendations.

"Obviously, ultimately the head of that department is responsible for it," Carney added. "But let's be clear there were numerous people involved who were career professionals and worked on those kinds of issues every day."

Hazel O'Leary, who served as Energy secretary for President Bill Clinton's entire first term, said that despite Chu's impressive resume, Obama's transition team advisers might not have gotten it right when they picked him to run the department.

"Generally, if you're in the first administration, the people advising the senior folks in the White House about how to place folks in jobs have very little understanding about what the challenges of the job are," she told POLITICO.

An environmentalist with close ties to the Obama administration said Chu didn't help his cause with his own staffing decisions, picking people with science and technical backgrounds over people with solid political and policy chops.

"On some levels, it's exactly what you'd like to believe to be the best team, the environmentalist said. “But in the realities of this town these days, you need some people who have a different kind of intuition.

"The great irony, the big critique [with Solyndra] is the suggestion of too much politics and political influence, when in fact the realities on this might be exactly the opposite, that there was too much science and too little intuition," the person added.